Starship Asterisk*

Image Credit: Yuri Beletsky (LCO)/ESO

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The otherworldliness of this image, obtained at ESO’s Very Large Telescope (VLT) in northern Chile, is due to a combination of natural and artificial light phenomena. This ethereal image captures a lunar halo on rare cloudy skies over ESO’s Paranal Observatory. This optical phenomenon is created when moonlight is refracted by millions of small ice crystals and water droplets in the surrounding atmosphere.

These haloes are reasonably common; however, they require quite a bit of light to appear, so the Moon must be in a specific position relative to the Earth and the Sun to reflect enough light to produce a fine ring like this one. This particular halo comprises multiple coloured bands that are formed in the same way as in a rainbow — light of different wavelengths is refracted by varying amounts. White light is thus broken into its constituent parts, dispersing to create a spectrum of visually distinct colours.

Image Credit: ESA/Hubble & NASA, R. Tully Acknowledgement: Gagandeep Anand

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The galaxy UGCA 193, seen here by the NASA/ESA Hubble Space Telescope, is a galaxy in the constellation of Sextans (The Sextant). Looking rather like a waterfall, UGCA 193 appears to host many young stars, especially in its lower portion, creating a striking blue haze and the sense that the stars are falling from “above”.

The blue colour of UGCA 193 indicates the stars that we see are hot — some with temperatures exceeding 6 times that of our Sun. We know that cooler stars appear to our eyes more red, and hotter stars appear more blue. As the mass and surface temperature of a star, and therefore its colour, are linked, heavier stars are able to “burn” at higher temperatures resulting in a blue glow from their surface.

Image Credit: ESO/G. Hüdepohl

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At first glance, this image looks both awesome and intimidating, with the enormous beams of light resembling some terrible cosmic weapon. Fortunately, that is not the case! This ESO Picture of the Week shows something far more benign — a mixture of gas, dust, and powerful lasers.

Among the largest nebulae in the southern night sky, the Carina Nebula is a perfect viewing target for ESO’s Very Large Telescope (VLT). In this image, the nebula appears as a stunning pink cloud in the clear sky above ESO’s Paranal Observatory in Chile, home of the VLT. The Carina Nebula is a vast cloud of dust and gas — this gas is ionised and made to glow by the stars within the nebula itself.

The cutting-edge Adaptive Optics Facility installed on one of the 8.2-metre Unit Telescopes (UTs) of the VLT is in full operation here. The orange laser beams are sent from the UTs into the atmosphere where they excite sodium particles, causing them to glow. This creates artificial ‘stars’ that can be used to measure the blurring effects caused by Earth’s atmosphere, which are then corrected by the telescope.

Image Credit: ESA/Hubble & NASA, S. Allam et al

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This NASA/ESA Hubble Space Telescope image features the galaxy LRG-3-817, also known as SDSS J090122.37+181432.3. The galaxy, its image distorted by the effects of gravitational lensing, appears as a long arc to the left of the central galaxy cluster.

Gravitational lensing occurs when a large distribution of matter, such as a galaxy cluster, sits between Earth and a distant light source. As space is warped by massive objects, the light from the distant object bends as it travels to us and we see a distorted image of it. This effect was first predicted by Einstein’s general theory of relativity.

Strong gravitational lenses provide an opportunity for studying properties of distant galaxies, since Hubble can resolve details within the multiple arcs that are one of the main results of gravitational lensing. An important consequence of lensing distortion is magnification, allowing us to observe objects that would otherwise be too far away and too faint to be seen. Hubble makes use of this magnification effect to study objects beyond the sensitivity of its 2.4-metre-diameter primary mirror, showing us the most distant galaxies humanity has ever encountered.

This lensed galaxy was found as part of the Sloan Bright Arcs Survey, which discovered some of the brightest gravitationally lensed high-redshift galaxies in the night sky.

Image Credit: ESO/Petr Horálek

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To the right of this image captured in northern Chile, the eye-catching arc of the Milky Way soars above the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. But despite the breathtaking view, the glow of our home galaxy is here rivalled by another type of interesting light.

The image also shows, on the arc to the left, a faint brightening of the night sky in the region of the ecliptic directly opposite the Sun. This phenomenon is known as gegenschein (German for “countershine”) and is created as interplanetary dust in the outer part of the Solar System — from comets and broken-up asteroids — scatters incoming sunlight.

In most parts of the world, phenomena such as gegenschein, or the stunning arc of the Milky Way, are masked by light pollution from artificial light sources. Some estimates indicate that over 80% of the world’s population lives under light-polluted skies, making sites like the Atacama Desert, where ALMA is located, all the more unique.

Image Credit: ESA/Hubble & NASA, R. Tully Acknowledgement: Gagandeep Anand

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Observed with the NASA/ESA Hubble Space Telescope, the faint galaxy featured in this image is known as UGC 12588. Unlike many spiral galaxies, UGC 12588 displays neither a bar of stars across its centre nor the classic prominent spiral arm pattern. Instead, to a viewer, its circular, white and mostly unstructured centre makes this galaxy more reminiscent of a cinnamon bun than a mega-structure of stars and gas in space.

Lying in the constellation of Andromeda in the Northern hemisphere, this galaxy is classified as a spiral galaxy. Unlike the classic image of a spiral galaxy, however, the huge arms of stars and gas in UGC 12588 are very faint, undistinguished, and tightly wound around its centre. The clearest view of the spiral arms comes from the bluer stars sprinkled around the edges of the galaxy that highlight the regions where new star formation is most likely taking place.